The present invention relates to a method for the automatic control of coordinate-measuring instruments and to means for carrying out the method.
Coordinate-measuring instruments are being increasingly used in repeated cycles of multiple measurement operations upon a massed succession of workpieces, for example under CNC control, during an unmanned night shift and without supervision by operating personnel, the massed succession being a large number of workpieces clamped on the machine table or fed continuously to the machine via a work-handling system. To control such an operation, a computer is loaded with a work program and continuously issues various other technical commands to the measurement machine; illustratively, these commands concern the probe-pin combination or configuration to be substituted, the contact force selected for the measurement, etc. And the computer receives and stores the measured coordinate values and status reports from the control electronics of the measurement machine.
If disturbance or interruption occurs during such an automatic CNC-controlled operation, an error signal can develop if the probe head has collided with an obstacle or if a correct measurement value cannot be retaken, due to too short an approach path or to a dirty surface of the workpiece. In accordance with the previously known state of the art, the CNC operation is interrupted upon the occurrence of such an error event, a warning signal is given, and the machine must be restarted manually by the operator after the error has been eliminated. Such interruptions in operation are undesirable since a measurement job can be thereby delayed for several hours.